This invention relates to a method of forming a fine resist pattern with ionizing radiations for use in the preparation of semiconductors, magnetic bubble elements, and to optical elements and a resist utilized to form such patterns.
In the manufacture of fine patterns for preparing semiconductor elements ultraviolet ray lithography utilizing a photoresist has generally been used. However, with increase in the packing density of integrated circuits of the semiconductor elements, extremely fine resist patterns are required, so that prior art lithography utilizing a photoresist can not satisfy such requirement.
To solve this problem, lithography utilizing electron beams, X rays or far ultraviolet rays has been proposed, and various resist materials for use in this technique have been developed.
Generally, such polymer type resists as polymethyl methacrylate (PMMA) and polybutene sulphone (PBS) have excellent resolution and can form fine resist patterns. At present, however, when semiconductor substrates are etched by using resist patterns formed on silicone oxide films having a thickness of 1 to 2 microns it is impossible to form satisfactory oxide film patterns. More particularly, in a dry etching process, it has been impossible to form satisfactory patterns because the resistance of PMMA and PBS resists against plasma and ions is not sufficiently high, and moreover, the etching speed of resist films is high. In a wet etching process utilizing hydrofluoric acid type etching solution, the adhesive force between a resist film and an oxide film is not high so that the amount of side etching becomes large thus failing to form satisfactory patterns.
On the other hand, among negative resists, there be mentioned a copolymer of glycidyl methacrylate and ethylacrylate which has an excellent etchant resistant property, but the resolution of such negative resist is poor. Moreover, due to the presence of the residue of the resist or scum it is impossible to form satisfactory resist patterns. As described above, it has long been desired to obtain a resist material capable of forming a fine resist pattern having high resolution and also capable of forming a satisfactory etching pattern by etching an oxide film formed with the resist pattern.